Sound amplifying or concentrating horn



Dec. 13, 192 7.

C. P. ALEXANDER SOUND AMPLIFYING OR CONCENTRATING HORN Filed Sept'. 22, 1925 lit Patented Dec. 13, 1927.

UNETED STATES Arnr CHARLES KP. ALEXANDER, E AKRON, OHIO.

Application filed. September 22, 1925. Serial No. 57,811.

This invention relates to acoustical ap scribed and claimed, and illustr paratus, particularly to sound amplifying and concentrating devices and has for its object the provision of a horn having a certain peculiar curvature which will provide a more perfect amplification or resonance than is ordinarily accomplished.

It is a matter of scientific knowledge that sound waves travel or move outwardly from the point of origin or generation in ever increasing spheres. It, therefore, becomes an object of the present invention to construct an amplifying horn or equivalent device having a curvature corresponding to the progression of the waves in accordance with this principle, the curve being what is known as a conchoid. In nature, such a curve occurs in the conch shell and it is known that shells of this type possess high amplifying power to the extent that trumpets and other similar devices have been constructed from them. Furthermore, use has been made of such shells in connection with phonographs, radio apparatus and the like to replace the ordinary type of tone chamber. rlowever, such shells possess many features of disadvantage as will be readily understood though having desirable amplifying qualities.

More specifically, the object of the invention is to provide an amplifying horn having a conchoid curve and capable of use for a wide variety of purposes either for the amplification of sound waves or for the concentration and reception thereof, the principle involved being equally adaptable to instruments such as megaphones, horns for radio loud speakers, phonographs, sirens, musical wind instruments, and also in connection with apparatus designed for assisting in concentrating sounds for making of phonographic records, for radio broadcasting, and for assisting the hearing of deaf persons and such other applications as have to do with the concentrating of sound.

Another object of the invention is to provide an amplifier or concentrator, as the case may be, which need not he of unusual size concentrator or condenser having a conchoid curve developed as will be hereinafter deated in the accompanying drawings in which: i

Figure 1 is a longitudinal section through horn constructed in accordance with the invention,

Figure 2 is a diagram showing the development of the curve.

Primarily, it should he stated that a con choid curve is the locus generated. by the intersection ot a circle with secant line pas ing through its center and a fixed point as the center of the circle moves along a fixed line. in developing this curve, reference is had to Figure 2 wherein the line OX is known as the directrix. The point A is called the pole and the radius O? the modulus. This radius is emual to the line GB. The shape of the curve is determined by the ratio of OE to 0A and it will, therefore, be observed that horn having such a curve, with the same size of hell, but shorter in length, may he made by shortening the dis-- tance between the points 0 and A. The algebraic formula for the development of the curve is expressed as follows:

r W, where Z) equals 021 and where a equals OB. In other words, sev "al circles or arcs having the same diam-ct. or radius are so consoructed or drawn as to have their centers Q O 0*, O 0, and O in the fixed line or directrix OK and then secant lines are drawn in such manner as to pass through the fixed point A and the several centers 0 to O in the intersecting relation to the successive arcs to define the points P, P P P P P P and P at which'the intersections of the arcs or circles with the secant lines take place. A line drawn through the point B, P, P P P P P P andP will define the conchoid curve.

In Figure 1 I have illustrated an actua horn 1 having its inner surface curved in accordance with the conchoid curve developed as indicated in Figure Obviously, there are no particular limitations as to the size of the horn or the material from which it is constructed though in the present instance it is represented as having a smooth inner surface :2 and a rough outer surface 3 which is not necessarily of uniform thickness, it

being conceivable that the uneven thickness will tend to prevent. vibration of the horn itself so that the sound waves issuing from the hell i will be free from distortion.

Experiments have been conducted with a horn having such a curve as disclosed and very remarkable results have been noted not only in regard to the amplification of sound but also when the device is used for concentrating or condensing and consequently magnifying sounds as for instance in connection with instruments tending to improve the hearing of deaf persons. \Vhen a horn construoted in this manner and having this curve has been used in connection with ox.- to form part of a radio loud speaker, it has been discovered that the purity and clear ness of tone are unexcelled and the volume everythingthat could be desired.

While I have shown and described a horn adapted to be used for various purposes and while I have shown a certain conchoid curve, it should be understood that the disclosure is merely illustrative'ot' the principle involved as the right is reserved to embody the principle in any particular mechanical device whatsoever and to make any and all such changes in every particular as will not depart from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim:

1. An acoustical device having its inner surface formed as a conchoid curve along); every line of longitudinal section, the curve having a straight line directrix or axis.

2. A sound wave amplifier having its in nor surface formed as a conchoid curve, the amplifier being circular at every line of transverse section and huviinr a straight line diroctrix.

In testimony whereof I aliix my sigma turc.

CHARLES l. ALEXANDER. 

